Organic Electronic Device and Dopant for Doping an Organic Semiconducting Matrix Material

ABSTRACT

An organic electronic device includes a substrate, a first electrode arranged on the substrate, at least a first functional organic layer arranged on the first electrode and a second electrode arranged on the first functional organic layer. The first functional organic layer includes a matrix material and a p-dopant with regard to the matrix material, wherein the p-dopant includes a copper complex containing at least one ligand.

This application claims the benefit of U.S. Provisional Application No.61/243,927, filed on Sep. 18, 2009, entitled “Organic Electronic Deviceand Dopant for Doping an Organic Semiconducting Matrix Material,” whichapplication is hereby incorporated herein by reference.

TECHNICAL FIELD

The disclosure relates to an organic electronic device that contains acopper complex as a p-dopant for doping an organic semiconducting matrixmaterial used for a functional organic layer comprised in the organicelectronic device. The disclosure further relates to a dopant for dopingan organic semiconducting matrix material wherein the dopant is apolynuclear copper complex.

BACKGROUND

It is known to modify organic semiconductors with regard to theirelectrical characteristics, especially their electrical conductivity, bydoping them. The doping leads to an increase in the conductivity ofcharge transport layers, thus reducing ohmic losses, and to an improvedpassage of the charge carriers within the organic layers.

Aspects of the invention solve the problem of providing p-dopants fordoping an organic semiconducting matrix material, especially formanufacturing organic electronic devices, preferably dopants which causean effective increase in the number of charge carriers in the matrixmaterial.

An organic electronic device according to the disclosure comprises asubstrate, a first electrode arranged on the substrate, at least a firstfunctional organic layer arranged on the first electrode and a secondelectrode arranged on the first functional organic layer. The firstfunctional organic layer of this device comprises a matrix material anda p-dopant with regard to the matrix material; the p-dopant comprises acopper complex containing at least one ligand L of the followingformula:

wherein E₁ and E₂ may be the same or different and represent oxygen,sulfur, selenium or NR′, wherein R represents a substituted orunsubstituted hydrocarbon, which may be branched, linear or cyclic, andwherein R′ represents hydrogen or a substituted or unsubstituted,branched, linear or cyclic hydrocarbon; R′ may also be connected with R.

Thereby, the fact that one layer or one element is arranged or applied“on” or “above” another layer or another element can mean here andhereinafter that one layer or one element is arranged in directmechanical and/or electrical contact on the other layer or the otherelement. Furthermore, it can also mean that one layer or one element isarranged indirectly on or respectively above the other layer or theother element. In this case, further layers and/or elements can then bearranged between one and the other layer.

Thereby, the first functional organic layer can particularly be selectedfrom the group comprising one or a plurality of electroluminescentlayers (EL), electron blocking layers (EBL), hole transport layers (HTL)and hole injection layers (HIL). Any further functional organic layercan be selected from the group comprising one or a plurality of electroninjection layers (EIL), electron transport layers (ETL), hole blockinglayers (HBL), electroluminescent layers (EL), electron blocking layers(EBL), hole transport layers (HTL) and/or hole injection layers (HIL).The recombination of electrons and holes leads to theelectroluminescence. Individual layers can also have functionalities ofa plurality of the aforementioned layers. Thus, a layer can serve, forexample, as HIL and as HTL or as EIL and as ETL.

The functional layers can comprise organic polymers, organic oligomers,organic monomers, organic small, non-polymeric molecules (“smallmolecules”) or combinations thereof.

According to the disclosure it was observed that copper complexes withligands L being carboxylates, homologues of carboxylates and therespective amides and amidinates may improve the whole transport in afunctional organic layer, i.e., the hole-conductivity of the layer isincreased by the dopant. If the organic electronic device is a radiationemitting device (for example, an OLED), surprisingly, these dopantsusually do not quench radiation emission. Usually, particularly thecopper(I) complexes even exhibit luminescence by themselves and can helpto detect loss channels in the device fabrication. It was observed forthe first time that a radiation emitting compound can also be used toincrease hole-conductivity. A further advantage of the present coppercomplexes is that the starting materials for these complexes aregenerally of low cost.

The copper complex of the present disclosure serves as a p-dopant;therefore, the copper complex is a metal organic acceptor compound withrespect to the matrix material of the first functional organic layer.Normally, the copper complex is a neutral (electron-poor) complex andhas at least one organic ligand L, without being restricted to that.

The copper complexes in the first functional organic layer may beisolated molecules. However, usually these copper complexes areconnected to molecules comprised in the matrix material by chemicalbonds (i.e., the molecules comprised in the matrix material serve asligands coordinating to the copper complex). Normally, the copper atom(or all of the copper atoms) are coordinated to organic ligands only.However, the organic ligands may possess suitable functional groupswhich allow linking to form an oligomer or polymer.

In an embodiment the ligand L may be at least bidentate, tridentate ortetradentate, and may particularly contain at least one or two moietiesC(=E₁)E₂ with at least one, two, three, four or more of the donor atomsE₁ and E₂ of the ligands coordinating to the copper atoms of the presentp-dopant. Usually all donor atoms E₁ and E₂ coordinate to the copperatoms of the present complex. The C(=E₁)E₂-moiety usually has onenegative charge. However, in theory the not deprotonated carboxylic acid(its homologues and the respective amides and amidinates) can also serveas a ligand. In general, the ligand L of the present disclosurecontributes negative charges to the complex (i.e., one negative chargeper CE₂ group).

According to an embodiment, the copper complex of the present disclosureis (in the state where no matrix molecule coordinates to the copperatom) a homoleptic complex where only ligands L are coordinated to thecentral copper atom. Further, the copper complex (particularly thecopper complex containing only ligands L) is often, as long as nomolecule of the matrix material coordinates to the central copper atom,complex with square planar or linear molecular geometry, particularly ifcopper-copper interactions are disregarded. Upon coordination of amatrix molecule the geometry is usually altered and, for example, apentagonal-bipyramidal coordination geometry or a square pyramidalmolecular geometry results. Usually, in all alternatives described inthis paragraph the copper complex is still, as mentioned before, aneutral complex.

It shall be understood that previous definitions of the copper complexesand/or ligands apply to mononuclear copper complexes but also topolynuclear copper complexes. In polynuclear copper complexes the ligandL may bind to only one copper atom and also to two copper atoms (i.e.,bridging two copper atoms). If ligands L are contained which aretridentate, tetradentate or multidentate ligands, also more than twocopper atoms of the polynuclear copper complex may be bridged. In thecase of polynuclear copper complexes copper-copper bonds may existbetween two or more copper atoms. However, particularly as far as copper(I) complexes are concerned, usually no copper-copper bonds (of thecopper complexes without coordinating molecules of the matrix) areobserved. This may be proven by x-ray spectroscopy and by absorptionspectroscopy (which shows a square planar surrounding of the copperatoms, i.e., a copper atom surrounded by four organic ligands,particularly four ligands L or copper complexes with two coordinatedligands, particularly two ligands L, with a linear geometry of thecomplex). Copper(I) complexes often show cuprophilic Cu—Cu interactions;The Cu—Cu carboxylate bridged distances may very broadly vary from 2.5to 3.2 Å.

If polynuclear copper complexes are used, the organic electronic deviceand in particular the first functional organic layer exhibits animproved lifetime. Presumably, charges transported via the firstfunctional organic layer may cause a destabilizing effect with regard tothe copper complex. If, however, more than one copper atom is present inthe copper complex, the destabilizing effect is distributed on allcopper-atoms. Therefore, polynuclear complexes usually show an improvedstability compared to mononuclear complexes.

In an embodiment, the polynuclear copper complexes show a so-called“paddle-wheel” structure, particularly as far as copper (II) complexesare concerned. A paddle-wheel complex is a complex with usually twometal atoms, in the present case copper atoms, which are bridged by one,two, three, four or even more multidentate ligands, in the present caseusually two or most often four ligands L. Usually the coordination modeof all ligands (with respect to the copper atoms) is almost identical sothat, with respect to copper atoms and ligands L, at least one two-foldor four-fold rotation axis through two of the copper atoms contained inthe polynuclear complex is defined. Square planar complexes oftenexhibit an at least four-fold rotation axis; linear coordinatedcomplexes often show a two-fold rotation axis.

In an embodiment of the present application, the copper atom of themononuclear complex or at least a part of the copper atoms (usually allcopper atoms) of the polynuclear copper complex shows the oxidationstate +2. In these complexes the ligands are mostly coordinated in asquare planar geometry (in the state where no molecules of the matrixare coordinating to the copper atom).

In a further embodiment the copper atom in the mononuclear complex or atleast a part of the copper atoms (usually all copper atoms) of thepolynuclear complex are in the oxidation state +1. In those complexesthe coordination mode of the copper atom is mostly linear (as long as nomolecule of the matrix coordinates to the copper atom).

Complexes containing copper (II) atoms usually exhibit a better holetransport ability than complexes containing copper (I) atoms. Copper (I)complexes have a closed shell d¹⁰ configuration. Therefore, the effectoriginates primarily form the Lewis acidity of the copper atom. Copper(II) complexes have a not closed d⁹ configuration, thus giving rise toan oxidation behavior. Partial oxidation increases the hole density. Onthe other hand, complexes containing copper (I) atoms are oftenthermally more stable than corresponding copper (II) complexes.

In a preferred embodiment, the copper complex of the present disclosure(in the state where no molecules of the matrix are coordinated) isLewis-acidic. A Lewis-acidic compound is a compound which acts as anelectron pair acceptor. A Lewis-base, therefore, is an electron pairdonator. The Lewis-acidic behavior of the present copper complexes isparticularly related to the molecules of the matrix material. Therefore,the molecules of the matrix material usually act as a Lewis-base withrespect to the Lewis-acidic copper complexes.

A Lewis-acidic complex according to the present disclosure may also be acomplex as described before wherein a solvent molecule coordinates tothe central copper atom at the free coordination site described before.However, particularly the tested copper complexes described in theexamples below do not comprise a solvent molecule.

In the present disclosure the copper atom contains an open (i.e., afurther) coordination site. To this coordination sites the coordinationof a (Lewis-basic) compound, particularly an aromatic ring or a nitrogenatom of an amine component contained in the matrix material cancoordinate (see the following schemes 1 and 2):

However, also other groups different from aromatic rings or aminenitrogen atoms are possible as far as aromatic ring systems arecontained also hetero aromatic rings may coordinate to the copper atom.Often, a coordination of the nitrogen atom of an amine component isobserved.

In an embodiment of the present disclosure, the ligand L coordinating tothe copper atom contains a group R representing a substituted orunsubstituted hydrocarbon, which may be branched, linear or cyclic. Thebranched, linear or cyclic hydrocarbon may particularly contain 1-20carbon atoms, for example, methyl, ethyl or condensed substituents (likedecahydronaphthyl or adamantyl, cyclo-hexyl or fully or partlysubstituted alkyl-moieties). The substituted or unsubstituted aromaticgroups R may, for example, be phenyl, biphenyl, naphthyl, phenanthryl,benzyl or a hetero aromatic residue, for example, a substituted orunsubstituted residue selected from the heterocycles depicted in thefollowing:

In a further embodiment of the present disclosure, the ligand Lcoordinating to the copper atom contains a group R representing an alkyland/or aryl group wherein the alkyl, aryl or aralkyl group bears atleast one electron withdrawing substituent. The copper complex maycontain more than one type of carboxylic acids (mixed systems), amidesand amidinates, wherein the word “type” refers on the one hand to thesubstituent R and on the other hand to the hetero atoms being connectedto the copper.

An electron withdrawing substituent according to this disclosure is asubstituent which reduces the electron density at the atom to which theelectron withdrawing substituent is bound compared to the respectiveatom bearing a hydrogen atom instead of the electron withdrawingsubstituent.

The electron withdrawing groups may, for example, be selected from thegroup containing halogens (e.g., chlorine and particularly fluorine),nitro groups, cyano groups and mixtures of these groups. The alkyland/or aryl group may bear exclusively electron withdrawingsubstituents, for example, the aforesaid electron withdrawing groups orhydrogen atoms as well as one or more electron withdrawing substituents.

If ligands L wherein the alkyl and/or aryl groups bear at least oneelectron withdrawing substituent are used, the electron density at thecentral atom (s) of the copper complex can be reduced; therefore, theLewis-acidity of the copper complex can be increased.

The ligand L may, for example, be the anion of the following carbonicacids: CHal_(x)H_(3-x)COOH, particularly CF_(x)H_(3-x)COOH andCCl_(x)H_(3-x)COOH, (wherein x represents an integer from 0 to 3 and Halrepresents an halogen atom), CR″_(y)Hal_(x)H_(3-x-y)COOH (wherein x andy are integers and x+y=a number from 1 to 3 and wherein y is at least 1and Hal represents a halogen atom); the substituent R″ may be alkyl orhydrogen or an aromatic group, particularly phenyl; all groups describedbefore for the residue R″ may contain electron withdrawing substituents,particularly the electron withdrawing substituents mentioned before or aderivative of benzoic acid containing an electron withdrawingsubstituent (for example, ortho-, para- or meta-fluoro benzoic acid,ortho-, para- or meta-cyano benzoic acid, ortho-, para- or meta-nitrobenzoic acid or benzoic acids bearing one or more fluorinated orperfluorinated alkyl groups, for example, a tri-fluoro methyl group. Forexample, the ligand L may be the anion of the following carbonic acidR″—(CF₂)_(n)—CO₂H with n=1-20; R″ stands for the same groups as listedabove for R, particularly again a group bearing electron withdrawingmoieties (for example, fully or partially fluorinated aromaticcompounds). If the volatility of the ligand L is too high (which mayoccur, for example, if perflorinated acetates and propionates are used),the molecular weight and thus the evaporation temperature can beincreased, without losing too much Lewis acidity with respect to thetrifluoroacetate. Therefore, for example, fluorinated, particularlyperfluorinated, homo- and heteroaromatic compounds can be used asmoieties R and R″, respectively. Examples are the anions of fluorinatedbenzoic acids:

wherein the phenyl ring bears 1 to 5 fluorine substiutents (i.e.,x=1-5). Particularly the following substituents, which are strong Lewisacids, (or the corresponding substituents bearing chlorine atoms insteadof fluorine atoms) may be bound to the carboxylate group:

Furthermore, the anions of the following acid may be used as ligands:

wherein X may be a nitrogen atom or a carbon atom bearing, for example,a hydrogen atom or a fluorine atom. According to an embodiment threeAtoms X stand for N and two for C—F or C—H (triazine derivatives). Alsothe anions of the following acid may be used as ligands:

wherein the naphthyl ring bears 1 to 7 fluorine substiutents (i.e.,y=0-4 and x=0-3 wherein y+x=1-7).

According to an embodiment, ligands L having the following structure maybe used:

wherein E₁ and E₂ are defined as above, wherein Y₁, Y₂, Y₃, Y₄ and Y₅represent the same or different groups or atoms and wherein Y₁, Y₂, Y₃,Y₄ and Y₅ are independently selected from the following atoms and/orgroups: C—F, C—Cl, C—Br, C—NO₂, C—CN, N, C—N₃, C—OCN, C—NCO, C—CNO,C—SCN, C—NCS, and C—SeCN, particularly independently selected from thefollowing atoms and/or groups C—F, C—NO₂, C—CN, and N. Thus, all ringmembers beside the C-Atom connected to the CE₂ ⁻ group are selected fromthese atoms and/or groups. These ligands L may for example be selectedfrom the following ligands:

According to this embodiment also aromatic substituents R beingdifferent from substituents R deriving from six-membered rings, i.e.,from phenyl are possible, for example, substituents R deriving frompolycyclic aromats, for example, deriving from 1-nayphthyl and2-naphthyl. These ligands L may, for example, be selected from thefollowing ligands:

In particular, fluorine as electron withdrawing substituent is mentionedas copper complexes containing fluorine atoms in the coordinated ligandsmay be evaporated and deposited more easily. A further group to bementioned is the trifluoromethyl group.

In a further embodiment of the present disclosure, the group R′ (in thecase of amidinates one or both of the groups R′) is represented by asubstituted or unsubstituted, branched, linear or cyclic hydrocarbonwhich bears at least one electron withdrawing substituent. This electronwithdrawing substituent is defined as above with respect to the group R.

In an embodiment, the first functional layer is a hole-transport layer.The addition of the copper complex to the matrix material of thehole-transport layer results in an improved hole-transport compared tothe matrix material containing no p-dopant. This improved hole-transportmay be explained by the transfer of the hole (or a positive charge) fromthe molecules of the matrix material being coordinated to the coppercomplex to the copper atoms and vice versa. This transfer is depicted inthe following scheme 3 containing several mesomeric structures of acopper (II) complex (the ligands L or any other ligands or additionalcopper atoms contained in the copper complex being omitted for thepurpose of clarity).

If the device according to the present disclosure is a radiationemitting device, usually no exciton blocking layers between the lightemitting layer and the hole-transport layer acting as a first functionalorganic layer are necessary as no quenching occurs upon addition of thep-dopant to the hole-transport layer.

The matrix material of the hole-transport layer may be selected from oneor more compounds of the following group consisting of NPB(N,N′-bis(naphthalen-1-yl)-N,N′-bis(phenyl)-benzidine, β-NPB(N,N′-bis(naphthalen-2-yl)-N,N-bis(phenyl)-benzidine), TPD(N,N′-bis(3-methylphenyl)-N,N′-bis(phenyl)-benzidine),N,N′-bis(naphthalen-1-yl)-N,N′-bis(phenyl)-2,2-dimethylbenzidine,Spiro-TPD(N,N′-bis(3-methylphenyl)-N,N′-bis(phenyl)-9,9-spirobifluorene),Spiro-NPB(N,N′-bis(naphthalen-1-yl)-N,N-bis(phenyl)-9,9-spirobifluorene),DMFL-TPD(N,N′-bis(3-methylphenyl)-N,N′-bis(phenyl)-9,9-dimethylfluorene,DMFL-NPB(N,N′-bis(naphthalen-1-yl)-N,N′-bis(phenyl)-9,9-dimethylfluorene),DPFL-TPD(N,N′-bis(3-methylphenyl)-N,N′-bis(phenyl)-9,9-diphenylfluorene),DPFL-NPB (N,N′-bis(naphth-1-yl)-N,N′-bis(phenyl)-9,9-diphenylfluorene),Sp-TAD (2,2′,7,7′-tetrakis(m,n-diphenylamino)-9,9′-spirobifluorene),TAPC (di-[4-(N,N-ditolyl-amino)-phenyl]cyclohexane), Spiro-TTB(2,2′,7,7′-tetra(N,N-di-tolyl)amino-spiro-bifluorene), BPAPF(9,9-bis[4-(N,N-bis-biphenyl-4-yl-amino)phenyl]-9H-fluorene), Spiro-2NPB(2,2′,7,7′-tetrakis[N-naphthyl(phenyl)-amino]-9,9-spirobifluorene),Spiro-5(2,7-bis[N,N-bis(9,9-spiro-bifluoren-2-yl)-amino]-9,9-spirobifluorene),2,2′-Spiro-DBP(2,2′-bis[N,N-bis(biphenyl-4-yl)amino]-9,9-spirobifluorene), PAPB(N,N′-bis(phenanthren-9-yl)-N,N′-bis(phenyl)-benzidine), TNB(N,N,N′,N′-tetra-naphthalen-2-yl-benzidine), Spiro-BPA(2,2′-bis(N,N-di-phenyl-amino)-9,9-spirobifluorene), NPAPF(9,9-Bis[4-(N,N-bis-naphth-2-yl-amino)phenyl]-9H-fluorene), NPBAPF(9,9-bis[4-(N,N′-bis-naphth-2-yl-N,N′-bis-phenyl-amino)-phenyl]-9H-fluorene),TiOPC (titanium oxide phthalocyanine), CuPC (copper phthalocyanine),F4-TCNQ (2,3,5,6-tetrafluor-7,7,8,8,-tetracyano-quinodimethane),m-MTDATA (4,4′,4″-tris(N-3-methylphenyl-N-phenyl-amino)triphenylamine),2T-NATA(4,4′,4″-tris(N-(naphthalen-2-yl)-N-phenyl-amino)triphenylamine),1T-NATA(4,4′,4″-tris(N-(naphthalen-1-yl)-N-phenyl-amino)triphenylamine), NATA(4,4′,4″-tris(N,N-diphenyl-amino)triphenylamine), PPDN(pyrazino[2,3-f][1,10]phenanthroline-2,3-dicarbonitrile), MeO-TPD(N,N,N′,N′-tetrakis(4-methoxyphenyl)benzidine), MeO-Spiro-TPD(2,7-bis[N,N-bis(4-methoxy-phenyl)amino]-9,9-spirobifluorene),2,2′-MeO-Spiro-TPD(2,2′-bis[N,N-bis(4-methoxy-phenyl)amino]-9,9-spirobifluorene),β-NPP(N,N′-di(naphthalen-2-yl)-N,N′-diphenylbenzene-1,4-diamine), NTNPB(N,N′-di-phenyl-N,N′-di-[4-(N,N-di-tolyl-amino)phenyl]benzidine) andNPNPB (N,N′-di-phenyl-N,N′-di-[4-(N,N-di-phenyl-amino)phenyl]benzidine).

In a further embodiment, the first functional layer of the organicelectronic device of the present application may be an electron blockinglayer. If the copper complexes according to the present disclosure wereused in an electron blocking layer, even if matrix materials usuallyused for electron transport materials are contained, almost no electronconductivity was observed. As mentioned before, every matrix materialused in electronic organic devices may be the matrix material of thefirst functional layer being an electron blocking layer, even electrontransporting matrix materials. For example, the matrix material can be amatrix material usually used for electron blocking layers. The (electronconducting) matrix material can, for example, be selected from one ormore of the materials of the group consisting of Liq(8-hydroxyquinolinolato-lithium), TPBi(2,2′,2″-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole)), PBD(2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole), BCP(2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline), BPhen(4,7-Diphenyl-1,10-phenanthroline), BAlq(bis-(2-methyl-8-quinolinolate)-4-(phenylphenolato)aluminum), TAZ(3-(4-biphenylyl)-4-phenyl-5-tert-butylphenyl-1,2,4-triazole), CzSi(3,6-bis(triphenylsilyle)carbazole), NTAZ(4-(naphthalen-1-yl)-3,5-diphenyl-4H-1,2,4-triazole), Bpy-OXD(1,3-bis[2-(2,2′-bipyridine-6-yl)-1,3,4-oxadiazo-5-yl]benzene),BP-OXD-Bpy(6,6′-bis[5-(biphenyl-4-yl)-1,3,4-oxadiazo-2-yl]-2,2′-bipyridyl), PADN(2-phenyl-9,10-di(naphthalen-2-yl)-anthracene), Bpy-FOXD(2,7-bis[2-(2,2′-bipyridine-6-yl)-1,3,4-oxadiazo-5-yl]-9,9-dimethylfluorene),OXD-7 (1,3-bis[2-(4-tert-butylphenyl)-1,3,4-oxadiazo-5-yl]benzene),HNBphen (2-(naphthalen-2-yl)-4,7-diphenyl-1,10-phenanthroline), NBphen(2,9-bis(naphthalen-2-yl)-4,7-diphenyl-1,10-phenanthroline), 3TPYMB(tris(2,4,6-trimethyl-3-(pyridin-3-yl)phenyl)borane) and 2-NPIP(1-methyl-2-(4-(naphthalen-2-yl)phenyl)-1H-imidazo[4,5-f][1,10]phenanthroline).

In a further embodiment, the first functional layer is an emissionlayer. Therefore, the first functional layer comprises a matrixmaterial, the copper complex according to the disclosure and a lightemitting material; alternatively, the first functional organic layer maycomprise a light emitting matrix material and the copper complex. Intheory, the first functional organic layer according to this embodimentmay also contain a matrix material and the p-dopant (copper complex),wherein the p-dopant additionally serves as a light emitting substance.However, usually the intensity of the light emitted by the coppercomplexes according to the disclosure exhibits, with respect to thelight emitting materials used for OLEDs known by the skilled person, area relatively low intensity. Therefore, applications using thecopper-complexes/p-dopants according to the disclosure as light emittingmolecules will usually contain a further emitter layer and the emitterlayer containing the copper complex will only serve for changing thespectrum (or the color) of the emitted radiation.

As already outlined before, the matrix material of the first functionalorganic layer comprises an organic compound or consists of this organiccompound. Usually, at least a part of this organic compound coordinatesto the copper complex (i.e., the p-dopant according to the disclosure).Therefore, not all molecules of the organic material of the matrixmaterial coordinate to copper atoms. However, one and the same organiccompound may also coordinate to two or sometimes even more copper atoms.If the organic compound contained in the matrix material of the firstfunctional organic layer contains, as described before, two or morecoordination sites a part of which coordinates two copper atomscatenarian structures or netlike structures of a plurality of the coppercomplexes (as defined in claim 1) and a plurality of organic moleculesmay be formed.

The coordination of the organic compound may result from interactions ofσ-electrons and/or π-electrons of the organic compound with the copperatom. Usually the hole-transport ability is improved if the number ofcatenarian or netlike structures in the first functional layer isincreased. Therefore, also the increase of possible coordination sitesusually leads to an increase of hole-transport as the formation ofnetlike structures or catenarian structures is favored.

Furthermore, also the structure of the copper complex has an influenceon the propensity of coordination of the organic compound. The smallerthe substituents R of the ligand L are, the less shielded the freecoordination site of the copper atom is and the easier a coordinationsite of the organic compound will coordinate to the copper atom.Therefore, substituents R being linear alkyl groups may be used, if a“deshielding” of the copper atom is desired.

In an embodiment, the amount of p-dopant/copper complex contained in thefirst organic functional layer is 50% by volume with respect to thematrix material, for example, the amount of the p-dopant may be 30% byvolume or less. Often the amount of the p-dopant with respect to thematrix material will be at least 5% by volume and 15% by volume at themost. The concentration by volume can easily be observed by comparisonof evaporated matrix material and evaporated p-dopant if the firstfunctional organic layer is produced by simultaneous evaporation ofmatrix and p-dopant (the layer thickness for and after evaporation canbe measured). A variation of the amount of p-dopant can easily berealized by changing the temperature used for evaporation of the sourceof p-dopant and matrix material. In embodiments where no evaporation ofthe matrix material and the p-dopant is used, the respective proportionof p-dopant in weight percent (calculated by multiplication with thedensity of the respective material) can easily be calculated.

The organic electronic device according to the disclosure may, inparticular, be a radiation emitting device, for example, an organiclight emitting diode (OLED). The organic electronic device may furtherbe, for example, an organic field effect transistor, an organic solarcell, a photo detector, a display or in general also an opto-electroniccomponent. An organic electronic device containing the p-dopants/coppercomplexes according to the disclosure serving as components improvinghole-transport is particularly suited for organic electronic deviceswherein the efficiency strongly depends on a good hole-transport. Forexample, in an OLED, the generated luminescence is directly dependent onthe number of formed excitons. The number of excitons is directlydependent on the number of recombining holes and electrons. A goodhole-transport (as well as electron transport) gives rise to a high rateof recombination and, therefore, to a high efficiency and luminescenceof the OLED. Furthermore, the power efficiency increases, when a voltagedrop over the transport layers decreases. If the conductivity of thetransport layers is about 3 to 4 orders of magnitude higher compared tothe other layers in the stack, the voltage drop over the transportlayers will usually no longer be observable. The most “power” efficientdevice will usually be a device, where the voltage is dropped almostonly along the emitting layers.

In an embodiment of the present disclosure, the first functional organiclayer of the organic electronic device is obtainable (or obtained) bysimultaneous evaporation of the copper complex (p-dopant) and the matrixmaterial. The simultaneous evaporation of the copper complex and thematrix material enables an interaction of those molecules.

In an embodiment, the organic electronic device according to the presentdisclosure can be produced by the following method:

A) providing a substrate,

B) arranging a first electrode on the substrate,

C) arranging at least the first functional organic layer on the firstelectrode,

D) arranging a second electrode on the at least first functional organiclayer.

Preferably, the first functional organic layer is produced bysimultaneous evaporation of the copper complex according to the presentdisclosure and the organic compound of the matrix material. Uponevaporation of the copper complex, often dimeric species are observed inthe vapor phase. Therefore, complexes with the same type of ligands andthe same ligand/copper atom ratio show the same evaporation temperature.

In an embodiment, the electrodes arranged in step B), step D) or in bothsteps are patterned.

The present disclosure also provides a semiconducting material producedusing a copper complex (p-dopant) as described before. Usually thissemiconducting material is obtainable by combining a matrix material andthe aforesaid copper complex, particularly, by simultaneous evaporationof the matrix material and the copper complex.

Further, the objective of the present disclosure is achieved by a dopantfor doping an organic semiconducting matrix material comprising at leasttwo copper atoms, and at least one ligand L bridging the two copperatoms, wherein the ligand L is represented by the following formula:

wherein E₁ and E₂ and R have the meaning as described before. Inparticular, this polynuclear copper complex is a Lewis-acidic coppercomplex. According to an embodiment R does not in all coordinatedligands L represent CF₃. According to a further embodiment R in none ofthe ligands L represents CF₃.

In a further embodiment the copper complex comprises four, particularlyin a “four-membered” ring, or six copper atoms, particularly in a“six-membered” ring, or polymeric species comprising a plurality ofcopper atoms in a chain-like structure.

In a further embodiment, the polynuclear copper complex contains atleast one ligand L (and is, for example, a homoleptic complex) whereinthe substituent R of the ligand L contains at least two carbon atoms.

In a further embodiment the copper complex contains a mixed ligandsystem, for example, a mixture of aliphatic ligands (liketrifluoroacetate) and aromatic ligands (like perfluorobenzoate). Thesemixed systems may, for example, be obtained by partial substitution ofthe ligands of a homoleptic complex (for example, a homoleptictrifluoroacetate complex).

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages and advantageous embodiments and developments of thedisclosure will become apparent from the embodiments described below inconjunction with the figures.

In the exemplary embodiments and figures, identical or identicallyacting constituent parts may be provided in each case with the samereference symbols. The elements illustrated and their size relationshipsamong one another should not in principle be regarded as true to scale;rather, individual elements, such as, for example, layers, structuralparts, components and regions, may be illustrated with exaggeratedthickness or size dimensions for the sake of better representabilityand/or for the sake of better understanding.

FIG. 1 shows a schematic illustration of a radiation-emitting deviceaccording to an embodiment of the disclosure;

FIG. 2 shows the electrical characteristics of 4 mm² device containing ahole-transport material and the p-dopant according to the presentdisclosure;

FIG. 3 shows a spectrum indicating the stability of a device used for aspectrum in FIG. 2;

FIG. 4 shows the I-V characteristics of an electron conducting layerdoped with the p-dopant of the present disclosure;

FIG. 5A shows the I-V characteristics of NPB doped with severalcopper-benzoate complexes;

FIG. 5B shows the principle of numbering of the fluorine positions onthe benzoic ring of the copper-complex;

FIG. 6 shows the I-V characteristics of 1-TNata doped withCu₄(O₂C(2,3,4,5,6-F)₅C₆)₄;

FIG. 7 shows a photoluminescence spectrum of a hole-transport materialbeing undoped or doped with a p-dopant according to the presentdisclosure; and

FIG. 8 shows an x-ray structure of the compound Cu₆(O₂C(2,4-F)₂C₆H₃)₆.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

FIG. 1 shows a schematic view of one embodiment of the organicelectronic device being a radiation emitting device. From the bottom upthe following layer sequence is depicted: the bottom most layer is thesubstrate 1, for example, a transparent substrate, for example, asubstrate made of glass. The succeeding layer is an anode layer 2 whichmay be a transparent conducting oxide (TCO) for example,indium-tin-oxide (ITO). On top of the anode layer 2, a hole-injectionlayer 3 is arranged. On top of the hole-injection layer, ahole-transport layer 4 is depicted (particularly a hole-transport layerbeing the first functional organic layer according to the presentdisclosure containing the p-dopant/copper complex). On top of thehole-transport layer, an emitter layer 5 is arranged. On top of theemitter layer 5, a hole-blocking layer 6 is arranged followed by theelectron transport layer 7 and the electron injection layer 8. On top ofthe electron injection layer, the anode 9 is arranged, for example, anelectrode made of metal or a transparent material (giving rise to atop/bottom-emitter).

Upon applying a voltage between anode and cathode, a current flowsthrough the device inducing the release of photons in the emitter layer5 which leads the radiation emitting device in the form of radiation viathe transparent anode 9 and the substrate 1 and/or a transparentcathode. In an embodiment the OLED is emitting white light; theradiation emitting device, therefore, may contain an emitter layercomprising several light emitting materials (for example, blue andyellow or blue, green and red emitting substances); alternatively,several emitter layers comprising molecules emitting light in differentcolors may be contained. Alternatively a radiation converting materialmay be contained in the light path.

The OLED shown in FIG. 1 may be produced by sputtering the anodematerial onto the substrate and subsequently adding the functionallayers by evaporation (co-evaporation) of the corresponding materialsand/or spin coating.

The device shown in FIG. 1 may also be altered in a way that the layersequence between anode and cathode is inverted (therefore, the cathodeis arranged on the substrate) and a top-emitting device, ifnon-transparent material is used for the cathode, is obtained.

In more detail, an OLED according to the present disclosure can beobtained by the following procedure.

An ITO pre-structured glass substrate is treated with oxygen plasma forten minutes and transferred into an evaporator as fast as possible. Theevaporator is located inside an argon filled glove-box with oxygen andwater concentration being less than 2 ppm. The pressure inside theevaporator is lower than 2×10⁻⁶ mbar.

Two sources, containing the matrix material and the p-dopant aresimultaneously heated up to a temperature just below the evaporationtemperature. The p-dopant and the matrix materials are then heated upfurther until a constant evaporation rate is reached. A shutter(inhibiting a deposition of the matrix material and the p-dopant) isopened for the co-evaporation. As a p-dopant, for example, Cu₂(O₂CCF₃)₄and Cu₄(O₂CCF₃)₄ may be used. Cu₂(O₂CCF₃)₄ is heated up to a temperatureof 144° C. yielding in an evaporation rate of 0.14 Å/s; Cu₄(O₂CCF₃)₄ isheated up to temperature of 81° C. yielding in an evaporation rate of0.10 Å/s.

The temperatures for evaporation are strongly dependent on the setupinside the evaporator and the evaporator used for the deposition. Themeasured temperature, e.g., strongly depends on the position of thethermocouple used for temperature measurements and further setupspecifications for every evaporator. All depositions mentioned in thisdisclosure were done with the same evaporator. The deposition rates canbe reproduced easily within a different evaporator due to calibration ofsensors.

As matrix materials, for example, the hole-transporting material NPB andthe electron transporting material BCP may be used. NPB is heated up toa temperature of 90° C. yielding in an evaporation rate of 2 Å/s; BCP isheated up to a temperature of 74° C. yielding in an evaporation rate of2 Å/s. Evaporation temperatures and evaporation rates are usuallyequipment dependent.

Subsequently, the sources are cooled down below 40° C. before theevaporation chamber is vented with argon and opened to change the maskfor the cathode deposition. The counter electrode is deposited bythermal evaporation and consists of a 150 nm thick layer of aluminum.The deposition is started (shutter opened) when the evaporation ratereaches 0.5 Å/s and the rate is then increased slowly up to 5 Å/s.

The obtained layer sequence is kept inside an inert atmosphere to recordthe spectrum according to FIGS. 2 to 4 right after the cathodedeposition.

FIG. 2 shows a current-voltage (I-V) characteristic of a layer sequenceas described before with a 200 nm thick layer of NPB of an 4 mm² device.The lowest curve in FIG. 2 depicts the electrical characteristic of anundoped NPB layer (diamonds); the curve in the middle is obtained by thesame arrangement containing additionally 5% by volume of Cu₄(O₂CCF₃)₄(triangles). The electrical characteristics show enhancement inconductivity by about seven orders of magnitude. In a third experimentthere are 200 nm thick layer of NPB is doped with 7% by volume ofCu₂(O₂CCF₃)₄ (squares). The electrical characteristics show enhancementin conductivity by about eight orders of magnitude.

Therefore, the present disclosure in general gives rise to anenhancement in conductivity of at least five orders, usually more thanseven orders of magnitude compared to an undoped hole-transport layer.

Furthermore, the spectrum depicted in FIG. 2 demonstrates that theinjection properties become independent from the work function of thematerial used for the anode. Aluminum and ITO exhibit the same behavior.Positive voltages indicate hole-injection from ITO, negative voltagesfrom aluminum, respectively.

In FIG. 3 the stability of a device containing a 200 nm thick layer ofNPB doped with Cu₄(O₂CCF₃)₄. The same device as described above (FIG. 2)was electrically stressed for 700 hours with a current of 1 mA. Duringthe whole testing time the necessary voltage to be applied does notsignificantly change.

FIG. 4 shows the I-V characteristics of the same layer sequence asdescribed before with the difference that an electron transportingmaterial instead of hole-transporting material is used. For all samplescorresponding to FIG. 4 a 200 nm thick layer of BCP was used. BCP is awell known electron conductor. The I-V characteristics of undoped BCPare shown as top most spectrum in FIG. 4 (diamonds). Upon doping the BCPlayer with 5% by volume Cu₄(O₂CCF₃)₄ (triangles) and 7% by volumeCu₂(O₂CCF₃)₄ (squares), respectively, the conductivity of the sampledrops to values around the noise level. Therefore, the p-dopantsaccording to the present disclosure do not promote electron conductivityin typical electron conductors, particularly electron conductors basedon nitrogen containing aromatic systems; they even prohibit electronconduction.

Seven copper(I)-benzoates were tested as p-dopants in NPB. FIG. 5A showsthe I-V characteristics of eight single-carrier-devices prepared asdescribed before by co-evaporation of NPB and the respective coppercomplex.

Six of these compounds were fluorinated ligand L and the position andquantity of fluorine was varied to investigate the effect on doping. Thelast compound is non-fluorinated as a kind of reference and to show thedifference between fluorinated and non fluorinated complexes. FIG. 5Bshows the principle of numbering of the fluorine positions on thebenzoic ring of the copper-complex of the seven compounds that have beeninvestigated.

Each device consists of a 200 nm doped organic layer sandwiched betweenthe ITO and aluminum (150 nm) electrodes. Compared to the NPB reference(diamonds) in FIG. 5A, there are two groups of benzoates yielding indifferent results.

A first group comprises of Cu₄(O₂CC₆H₅)₄ (squares),Cu₆(O₂C(2,6-F)₂C₆H₃)₆ (circles) and Cu₄(O₂C(4-F)C₆H₄)₄ (asterisks) whichall show a much lower (3 orders of magnitude) current density forpositive voltages compared to NPB and no improvement (drop) of thebuild-in voltage (no shift towards lower voltages). For the firstcompound of this group this effect is probably due to the lack offluorine which seems to be required for a sufficient doping effect. Eventhough the other two materials contain fluorine, its position andquantity seems to avoid a doping effect. The second compound containstwo fluorine atoms on the ring on positions 2 and 6 and are thereby onthe “inside” of the compound hindering the electron pulling effect offluorine and therefore reduce the hole generation possibility on thecopper atom and its doping effect. The third compound of this group hasone fluorine atom located on position 4 which is on the “outside” of thestructure, but the quantity of fluorine is too low to obtain a suitabledoping effect.

A second group comprises of four compounds with an increasing quantityof fluorine and a shift of fluorine towards the outer positions of thecopper-benzoate structure.

Cu₄(O₂C(3-F)C₆H₄)₄ (crosses), Cu₆(O₂C(3,5-F)₂C₆H₃)₆ (plusses),Cu₄(O₂C(3,4,5-F)₃C₆H₂)₄ (dashes) and Cu₄(O₂C(2,3,4,5,6-F)₅C₆)₄(triangles) all have a similar behavior for positive voltages. Thecurrent densities with these materials doped into NPB do not drop by 3orders of magnitude as for the first group but are within one order ofmagnitude compared to the NPB reference which is considered to beequivalent. None of those materials increase the current density forhigher (4-5 V) positive voltages nor do any of them show a classicalsymmetrical doping characteristic as copper-trifluoroacetate. However,all of these materials shift the build-in voltage towards lower voltagesand thereby increase the current density for lower voltages (0-1 V) andthereby show a kind of doping effect even though it is not as strong asin copper-trifluoroacetate complexes. The factor of position andquantity of fluorine is clearly shown as “outer” positions and morefluorine atoms increase the effect of voltage reduction. Furthermore thebest tested material Cu₄(O₂C(2,3,4,5,6-F)₅C₆)₄ (triangles) shows araised characteristic for negative voltages and indicate a possiblesymmetry which indicates a doping effect. The legend in FIG. 2 is sortedfrom the reference NPB (top) to the best of the eight tested materialsCu₄(O₂C(2,3,4,5,6-F)₅C₆)₄ (bottom).

Based on these results another test was done to investigate the dopingeffect of this new group (copper-benzoates) with another matrixmaterial. In general the possibility of doping does not only depend onthe dopant, but also on the potential ionization of the matrix material.The lower the HOMO-level (Highest Occupied Molecular Orbital) the easierit is to ionize the material. NPB as the first reference matrix materialhas a HOMO level of −5.5 eV and therefore a material with a lower HOMOwas chosen: 1-TNata(4,4′,4″-Tris(N-(1-naphthyl)-N-phenyl-amino)triphenylamine) with a HOMOof −5.0 eV was used to prepare a similar single carrier device bycoevaporation as mentioned before. FIG. 6 shows the I-V characteristicsof a single carrier device with 1-TNata doped withCu₄(O₂C(2,3,4,5,6-F)₅C₆)₄ (triangles) and a 1-TNata reference graph(diamonds). As illustrated the characteristic shows an enhancementincurrent density of two orders of magnitude for positive voltages. Thesymmetrical behavior of this graph (triangles) also shows theindependence of the metal work functions of ITO and aluminum. Thissingle carrier device shows a very clear and classical doping effect forthe given matrix-dopant combination.

FIG. 7 shows the photoluminescence spectrum of NPB doped withCu₄(O₂CCF₃)₄. NPB itself exhibits a blue fluorescence with a maximumaround 440 nm. The copper complexes according to the present disclosure,particularly the copper(I) trifluoroacetate complex described before,shifts the emission of NPB towards the ultraviolet region. Upon dopingNPB with Cu₄(O₂CCF₃)₄ the emission maximum of NPB is shifted to around400 nm. The emission of the copper complex itself is visible at around580 nm at room temperature (upon excitation with UV radiation,λ_(ex)=350 nm). In general, the copper(I) complexes according to thepresent disclosure show an emission maximum between 500 nm and 600 nm.In the following examples for the preparation of the copper complexesaccording to the present disclosure are described:

1. General Synthesis Starting from Copper(I) Oxide

Cu₂O and an anhydride of the respective carboxylic acid (in excess, forexample, two-fold excess with respect to a molar ratio ofcopper:carboxylic acid of 1:1) mixed with a suitable solvent andrefluxed over night. Cu₂O having not reacted is removed by filtration.The solvent is evaporated and the obtained material heated under vacuumat elevated temperature for at least ten hours. The obtained materialmay be purified by sublimation.

If no anhydride of the carboxylic acid is available, also the carboxylicacid itself and water trapping material (for example, DEAD) may be used.

2. Synthesis of Unligated Cu₄(O₂CCF₃)₄

Cu₂O (0.451 g, 3.15 mmol) was added and 2 ml of (CF₃CO)₂O, followed by30 ml of benzene. The mixture was refluxed over night to give a bluesolution and some unreacted starting material. This suspension wasfiltered through celite to remove the Cu₂O. The blue solution was thenevaporated to dryness, affording a very pale blue solid. It was heatedat 60° C. to 70° C. under vacuum for 10 to 15 hours to give the desiredproduct. Yield: 64%. Crystalline material is obtained by sublimation ofthe crude solid at 110° C. to 120° C.

3. Synthesis of Cu₄(O₂CC₆H₅)₄

Benzoic acid (2.5 g, 10.24 mmol) was heated under nitrogen for two hoursin refluxing xylenes (14 ml) in a Dean-Stark apparatus. The obtainedsolution was added to a copper (I) oxide (0.2 g, 1.40 mmol) and refluxwas continued until all the oxide had reacted (approximately 12 hours).Upon slow cooling to room temperature, the product started to appear asa white crystalline precipitate while benzoic acid remained in thesolution. After two and a half hours and thirteen minutes the solutionwas removed by a canula. The polycrystalline powder was washed withxylenes (3 times 20 ml) and dried under vacuum. Yield: 75%.

In this example a Dean-Stark apparatus is used instead of a watertrapping material.

4. General Synthesis of Copper(I) Complexes Starting from Cu₄(O₂CCF₃)₄

Cu₄(O₂CCF₃)₄ and an at least five-fold excess of a carboxylic acid to becoordinated to the copper atoms are combined with a suitable solvent andrefluxed for at least 12 hours. The obtained solution is evaporated todryness and heated at elevated temperature under vacuum for several daysto remove the excess of unreacted acid. Pure product may be obtained bysublimation.

5. Synthesis of Cu₄(O₂C(3-F)C₆H₄)₄

Cu₄(O₂CCF₃)₄(0.797 g, 1.13 mmol) (3-F)C₆H₄COOH (0.945 g, 6.75 mmol) areloaded in a Schlenk flask inside a glove box and 55 ml of benzene wasadded to the mixture. A homogenous light blue solution was refluxed overnight and then evaporated to dryness to afford a very pale blue solid.It was heated at 90° C. to 100° C. under vacuum for several days toremove the excess of unreacted acid. Air stable colorless blocks wereobtained by sublimation-deposition of the crude powder at 220° C. in oneweek. Yield: 65%.

6. Synthesis of Unligated Cu₂(O₂CCF₃)₄

Commercially available Cu(O₂CCF₃)₂*n H₂O (0.561 g, 1.94 mmol) wasdissolved in 3 ml of acetone to give an intensely blue suspension.Filtration and removal of all volatiles under reduced pressure affordeda blue-green residue, which was kept under a dynamic vacuum at 70° C. to80° C. for 34 hours to give a green solid. Yield: 87%.

7. General Synthesis Starting from Copper(II) Oxide

Alternative A) Copper(II) oxide is reacted with an excess of acorresponding acid (for example, pivalic acid, HOOCC(CH₃)₃)) uponheating (molar ratio, for example, Cu:HL=1:5). A crystalline productprecipitates after the solution is allowed to cool down. The solids arethen filtered and dried. They may, contain coordinated carboxylic acids,but recrystallization from anhydrous acetone followed by drying undervacuum, as described in example 7, yields unligated copper(II)carboxylates (see also S. I. Troyanov et al., Koord. Khimijya, 1991, vol17, N12, 1692-1697).

Alternative B)—electrochemical synthesis of copper(II) carboxylatesaccording to K. Kushner et al., J. Chem. Ed. 2006, 83, 1042-1045.

8. Synthesis of Cu₆(O₂C(2,4-F)₂C₆H₃)₆.

A mixture of Cu₄(O₂CCF₃)₄ (0.75 g, 4.2 mmol) and 2,4-difluorobenzoicacid (0.840 g, 5.3 mmol) was loaded in a glove box into a 100 ml Schlenkflask. Then 50 ml of benzene was added to the flask. The reactionmixture was refluxed for 24 hours to afford a light blue solution with awhite precipitate. The product was filtered off and washed with benzene(three times 10 ml). It was then heated under reduced pressure at 80° C.to 90° C. for two to three days. The resulting solid was loaded into asmall glass ampoule, which was evacuated and sealed under vacuum.Crystals were obtained as small colorless blocks bysublimation-deposition procedures from the gas phase at 160° C.-190° C.Yield (single crystalline material): 0.439 g (47%).

FIG. 8 shows an X-ray structure of this compound. The lines between thecopper atoms do not represent copper-copper bonds.

The invention is not restricted by the description on the basis of theexemplary embodiments. Rather, the invention encompasses any new featureand any combination of features, which, in particular, comprises anycombinations of features in the patent claims, even if this feature orthis combination itself is not explicitly explained in the patternclaims for exemplary embodiments.

1. An organic electronic device, comprising: a substrate; a firstelectrode arranged on the substrate; at least a first functional organiclayer arranged on the first electrode; and a second electrode arrangedon the first functional organic layer, wherein the first functionalorganic layer comprises a matrix material and a p-dopant with regard tothe matrix material, wherein the p-dopant comprises a copper complexcontaining at least one ligand L of the following formula:

wherein E₁ and E₂ may be the same or different and represent oxygen,sulphur, selenium or NR′, wherein R represents hydrogen or a substitutedor unsubstituted, branched, linear or cyclic hydrocarbon, and wherein R′represents hydrogen or a substituted or unsubstituted, branched, linearor cyclic hydrocarbon.
 2. The organic electronic device according toclaim 1, wherein the copper complex is a polynuclear complex.
 3. Theorganic electronic device according to claim 2, wherein the at least oneligand L of the copper complex is bridging two copper atoms.
 4. Theorganic electronic device according to claim 1, wherein copper atomscontained in the copper complex are at least partially in an oxidationstate +2.
 5. The organic electronic device according to claim 1, whereina copper atom or copper atoms contained in the copper complex are atleast partially in an oxidation state +1.
 6. The organic electronicdevice according to claim 1, wherein the group R of the at least oneligand L represents an alkyl and/or aryl group bearing at least oneelectron withdrawing substituent.
 7. The organic electronic deviceaccording to claim 1, wherein the first functional organic layer is ahole transport layer.
 8. The organic electronic device according toclaim 1, wherein the first functional organic layer is an electronblocking layer.
 9. The organic electronic device according to claim 1,wherein the matrix material of the first functional organic layercomprises an organic compound and the organic compound partiallycoordinates to the copper complex.
 10. The organic electronic deviceaccording to claim 9, wherein the organic compound contains at least twocoordination sites and wherein the at least two coordination sites of atleast a part of the organic compound coordinate to a copper atom so asto form a catenarian structure or a netlike structure of a plurality ofcopper complexes and a plurality of molecules of the organic compound.11. The organic electronic device according to claim 1, wherein theorganic electronic device comprises a device selected from the groupconsisting of a field effect transistor, a solar cell, a photo detector,an optoelectronic component, a light-emitting diode and a display. 12.The organic electronic device according to claim 1, wherein the firstfunctional organic layer is obtainable by simultaneous evaporation ofthe copper complex and the matrix material.
 13. A polynuclear coppercomplex for doping an organic semiconducting matrix material comprisingat least two copper atoms, and at least one ligand L bridging the twocopper atoms, the ligand L having the following formula:

wherein E₁ and E₂ denote independent from each other oxygen, sulphur,selenium or NR′, wherein R′ represents hydrogen or a substituted orunsubstituted, branched, linear or cyclic hydrocarbon and wherein Rrepresents a substituted or unsubstituted, branched, linear or cylicalkyl or aryl group bearing at least one electron withdrawingsubstituent, and particularly represents fluorinated or perfluorinatedaromatic or aliphatic substituents, with the proviso that R does notrepresent CF₃.
 14. The polynuclear copper complex of claim 13,comprising 4 or 6 copper atoms.
 15. The polynuclear copper complex ofclaim 13, wherein R contains at least two carbon atoms.